In a large number of patent documents is published the production of a copper-based sintered alloy, in which the copper powder or the copper-alloy powder is mixed with hard powder to improve the wear-resistance and is sintered to produce sliding material. For example, it is published in U.S. Pat. No. 5,279,638 that the wear-resistance against the opposite sliding material having a rough surface is enhanced by means of adding, as the hard particles, Fe.sub.2 P, Fe.sub.3 P, FeB, Fe.sub.2 B, Mo, Co, Co-base self-fluxing alloy, Ni-base self-fluxing alloy, SiC, TiC, WC, B.sub.4 C, TiN, cubic BN, Si.sub.3 N.sub.4, NiO.sub.2, ZrO.sub.2, Al.sub.2 O.sub.3, Si-Mn, Cu-Si and/or FeS.
In addition, it is disclosed in Japanese Unexamined Patent Publication (kokai) No. 8-25,026 that: AlN has good adhesiveness with the copper-based sintered material and good sliding characteristics and the characteristics of AlN are not impaired by the hard particles listed in the preceding paragraph provided that the amount of addition of these hard particles is less than the amount of addition of AlN. As a result, satisfactory characteristics are obtained.
Furthermore, it is disclosed in Divulgation (Al) W096/27,685 to add 20% or less in total of Al.sub.2 O.sub.3, SiC, SiO.sub.2, Fe.sub.3 P, AlN, Si.sub.3 N.sub.4, TiC, WC, BN, NiB and/or FeB to a copper alloy which contains from 0.1 to 2% of Ag.
Sintered materials generally have surface roughness of from approximately 10 to 50 .mu.m, and such surface roughness is disadvantageous for forming the lubricating-oil film. The surface roughness of the sintered materials should, therefore, be further decreased. The method for decreasing roughness is usually carried out by machining with a turning tool and then, if necessary, finishing with a grinding wheel.
Although the wear-resistance of sliding materials is enhanced by the addition of the above-mentioned hard particles, when the surface of the sintered alloy is machined, the turning-tool, even a sintered diamond turning-tool having the highest hardness, is detrimentally worn. That is, a new problem is incurred in that the life of the turning tool is seriously shortened.
It is, therefore, an object of the present invention to provide a sintered sliding material, which is based on the addition of hard particles to the copper, and which does not incur the shortening the life of a cutting tool, while maintaining improved sliding characteristics due to the hard particles.